CdTe Quantum Dots Targeting In Living Cells And The Effects Of APX Mimics In Cardiac Muscle Cells

The plasma membrane is selectively permeable; it allows a very few molecules across it. The plasma membrane permeability greatly limited the application of most protein and peptide including some organic drug molecule, which can function as killing bacteria and virus. In recent years, it is found that some signal sequence of protein with biomacromolecular can penetrate the plasma membrane without energy or receptor. These sequences are called cell-penetrating peptide (CPP). Three biotinylated signal peptides (nuclear targeting sequences, NTS; endoplasmic reticulum targeting sequence, ETS; mitochondria targeting sequence, MTS), was designed and synthesized by SPPS. The signal peptides were coated with avidin CdTe quantum dots (QDs). The purified QDs~NTS and QD~ETS were observed targeting in nuclear and endoplasmic reticulum separately. Not only ATP, but reactive oxygen species (ROS) as a by-product of energy conversion, are synthesized in Mitochondria (MT). Usually, ROS can be reduced by such as Glutathione (GSH) and vitamin E. Superoxide dismutase (SOD), glutathione peroxidase (GPX) and Catalase can also reduce ROS. It is hard to reduce too much ROS by enzymes in MT under pathological state. The excess ROS always results in modifications in mitochondrial lipids, proteins and DNA, even necrosis and apoptosis. It is reported that ROS can result in many disease, such as heart failure, ischemic heart disease and Parkinson's disease. In addition, it is also reported that there was closer relationship between ROS and ageing。As the importance of cleaning ROS in MT and our study on anti-cataract by ascorbate peroxidase (APX) mimics (deuterohemin Histidine peptide-6, DhHP-6), MTS was linked with DhHP-6 by disulfide. The new molecular is named MTS~DhHP-6. The peroxidase activity of MTS~DhHP-6 (2.1x103 U·μmol-1) is similar to that of MP-11 (4.2x103 U·μmol-1). The MTS~DhHP-6 and DhHP-6 are both excellent mimics of APX. To investigate the anti-oxidative effect, an experimental model of oxidative injury, which was induced by H2O2 (100μmo l·L-1), was established by using cultured neonatal rat ventricular myocytes. MTS~DhHP-6 coated with QDs can accumulate into Neonatal rat cardiomyocytes (NRCMs) of Wistar line and co-locate with MitoTracker Red in MT. The anti-oxidative effects of MTS~DhHP-6 and DhHP-6 were investigated in the model of oxidative injury by trypan blue dye exclusion, MTT cell proliferation assay, LDH leakage and the express level of catalase RNA. The results show that MTS~DhHP-6 (5nmol·L-1) has more effective protective effects on anti-oxidative damage than that of DhHP-6 (5nmol·L-1) has. The catalase RNA express level of MTS~DhHP-6 treated group, detected by Real-Time PCR, is lower than that of DhHP-6 treated group. These resultsproved that MTS~DhHP-6 has excellent protective effects. MTS~DhHP-6 is an excellent APX mimics and has potential clinical use in the protection and therapy of the diseases caused by free radical damage.